It is known to blow mold fuel tanks from co-extruded six layer parisons that include inner and outer layers of HDPE, a vapor barrier layer sandwiched between a pair of adhesive layers, and a layer of regrind material between one of the adhesive layers and the outer layer. Wherever the vapor barrier layer is interrupted there is a potential path through which hydrocarbons can more easily escape to the atmosphere from the fuel tank. The vapor barrier layer may be interrupted in, for example, the area of openings through the fuel tank wall and in the area of the pinch or seam formed when the parison is closed for molding.
One opening in the fuel tank is provided to receive fuel into the fuel tank through a fill pipe that is attached to the tank via a fill nipple at one end, and receives a refueling nozzle of a refueling or gas station pump at its other end. Conventional fill nipples where made of monolayer HDPE that easily bonded to the fuel tank, but were not highly effective at reducing or inhibiting hydrocarbon permeation to the atmosphere.
In order to meet increasingly strict emission standards, largely promulgated by governmental agencies, it is desirable to form fuel tank and system components that contact liquid fuel or fuel vapor to limit fuel vapor emissions to the atmosphere.